The aging process affects the human body in many ways. One thing that happens to all of us as we age is muscle loss.

Some experts say muscle loss begins around age 50. But others say it can start as early as age 30.

The Harvard Health Publishing website notes that “after age 30, you begin to lose as much as three percent to five percent” of muscle every 10 years. They add that most “men will lose about 30% of their muscle mass during their lifetimes.”

Experts may not know exactly when muscles loss starts. But they do know this: being inactive can speed up the process.

Now, the good news! Lost muscles are not gone forever. Although muscle loss may be a natural part of aging, you can do some things to slow it down. It is better to start building muscles when you are younger and in good health. But it is never too late to start strength training.

But what exactly is “strength training”? Simply put, strength training is any activity that makes one’s muscles stronger. We will talk about those exercises a little later. But first, let us talk about some of the health benefits of strength training.

This information comes from Harvard Medical School and the Mayo Clinic, a nonprofit health and research organization in the United States. Here are reasons to start your strength training today.

Harvard University researchers say that strength training puts pressure on your bones. And that is a good thing. This pressure can increase the thickness or density of bones. This can reduce your risk of developing osteoporosis -- a disease that weakens bones, making them easy to break.

Osteoporosis affects men and women of all races. But the Mayo Clinic notes that “white and Asian women -- especially older women who are past menopause -- are at highest risk.”

Strength training can help you to take control of your weight and even lose weight. Muscle weighs more than fat. But muscle increases your metabolism, and a higher metabolism helps you burn more calories.

Strength training can improve your ability to do everyday activities. For example, having stronger muscles makes it easier to lift and move things.

Strong muscles can improve your balance. So, your risk of falling or getting injured may be lessened. As we age, this can greatly add to your quality of life.

Experts say strength training can reduce the problems of many chronic -- or long-term -- disorders, such as arthritis, back pain, heart disease, diabetes and depression.

The Mayo Clinic says some research shows that regular strength training, when combined with other kinds of exercise, may help older adults think and learn better.

Resistance material is rubbery. When you pull on it, it gives your muscles resistance. There are many kinds of resistance material. They do not cost much and are often sold in sporting goods stores.

Free weights, commonly used in strength training, are handheld weights. They are not connected to exercise equipment; so, we call them “free.” We also call them barbells or dumbbells. If you do not have free weights, you can use any heavy object that is safe to lift.

Many gyms and health clubs have weightlifting or resistance machines. Some people also buy these machines and set them up at home. But they can cost a lot of money.

Working with free weights or weightlifting machines can be riskier. If you are new to weight training, experts suggest working with a trainer or physical fitness specialist. This way you will learn the right way to move and avoid injury.

The Mayo Clinic has this warning for those wanting to start weight training. Its experts say you should talk with your doctor before beginning if you have a chronic health condition, are older than age 40, and have not been active recently.

If you are using weights, how much should you use? The right amount should tire muscles after 12 to 15 repetitions. You can slowly increase the amount as you get stronger.

Also listen to your body. If an exercise causes pain, stop the exercise. Experts say after the pain goes away you can try the exercise again, but with a lower weight.

You do not have to use special exercise equipment or go to a gym to do strength training. You can use your own body weight as resistance.

Exercises that use body weight as resistance are usually safer for beginners. They can also be easier on the body, and you can do them anywhere. Push-ups, plank poses, jumping jacks, side jumps and squats -- or deep knee bends -- are great exercises for making muscles stronger.

The experts also suggest warming up before strength training. Cold muscles injure more easily than warm muscles. Walking for five to 10 minutes is enough to warm up your muscles.

And give your muscles time to recover. They say to rest one full day between exercising each specific muscle group.

And do not forget that some foods help you build muscle. The body breaks down protein into amino acids, which it uses to build muscle. So, experts say eat a little healthy protein with each meal -- foods such as chicken, salmon, beans and yogurt.